Fred wrote:
That gives you nut retention, but doesn't ensure your nut stays tight. If the nut is under any serious load, having it back off will cause damage, possibly stud breaking damage.
Yamaha likes splined fold-over washers on the drive sprocket and clutch hubs, with high tightening torques and loads. Of course, you're talking a 20-25mm splined shaft with a thread for the retaining nut, not a 6mm bolt.